Optimal solution

So Sony's engineering team sought out another technique for its 27-inch prototype. "The [laser-annealing] technique is also attractive for combining white organic EL with color filters," Ishibashi said. Using a color filter can achieve ultrahigh density, because there is no mask required to pattern discrete red, green and blue subpixels. That lowers the cost of production, although the color purity decreases and power consumption rises.

The number of bad pixels won't change, regardless of panel size. "So we need to get rid of the causes of the bad pixel as best we can," said Takatoshi Tsujimura, senior director of the OLED product division at Kodak. "To realize this, the combined use of white organic EL and a color filter is the best approach."

According to Tsujimura, the luminescence efficiency improves twofold by installing white pixels to the conventional triad of RGB subpixels. "It's because no color filters are used for white pixels," he said. "Thus, nothing prevents white light from coming through 100 percent. This is how high efficiency is achieved."

Organic-EL panels are finding their way into applications other than displays, including solid-state lighting and solar cells. Kaneka, a diversified chemical manufacturer, last month said it would begin joint research with Osaka University on an OLED lighting device and an organic thin-film solar cell.

OLED's thinness, lightness and surface-emitting properties make it useful for illumination purposes. Thinness and light weight are particular advantages in automotive and aircraft applications.

"Organic ELs can already exhibit 50 lumens per watt; 100 lumens/W is expected to be realized in 2010," said Gidas Sorin, CEO of German company Novaled. In contrast, the highest efficiency of a light bulb is approximately 20 lumens/W.